Distribution of progesterone‐binding cytochrome P450 and steroid‐17α‐hydroxylase/C‐17,20‐lyase within different compartments of the rat testis

Kühn‐Velten, N.; Staib, W.

doi:10.1016/0014-5793(83)80877-1

Cited by 7 publications

(1 citation statement)

References 26 publications

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“…Aliquots of the original suspensions and of the aqueous supernatants were extracted with diethyl ether (93 %0 mean recovery), the total activities were counted, and the steroid fractions were separated by t.l.c. as described previously [28].…”

Section: Methodsmentioning

confidence: 99%

Specific accumulation of 17α-hydroxyprogesterone in microsomal membranes during the process of cytochrome P-450(C-17)-catalysed androgen biosynthesis. A dynamic study of intermediate formation and turnover

Kühn‐Velten

Lessmann

Förster

et al. 1988

Biochemical Journal

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A complete dynamic analysis of cytochrome P-450(C-17)-catalysed androgen biosynthesis from a single dose of progesterone and 17 alpha-hydroxyprogesterone in a double-label double-substrate experiment was performed in order to elucidate the controversial intermediacy of 17 alpha-hydroxyprogesterone. Label distribution within the steroid fractions as well as in the membrane and buffer compartments yields direct evidence that the endogenously formed 17 alpha-hydroxyprogesterone (which is in an 'intermediate state') accumulates to a higher degree in microsomal membranes than does the exogenously added 17 alpha-hydroxyprogesterone (which is in a 'substrate state') under certain conditions. It is also demonstrated that endogenously formed 17 alpha-hydroxyprogesterone may partly leave the membrane compartment (in terms of a 'leakage' or 'overflow' phenomenon) and is then able to equilibrate with the pool of exogenously added 17 alpha-hydroxyprogesterone. Since only the label distribution in the membrane-associated (but not always in the aqueous) 17 alpha-hydroxyprogesterone pool corresponds to the label distribution in the androgen fraction, it is concluded that only the membrane-associated 17 alpha-hydroxyprogesterone pool is directly accessible to cytochrome P-450(C-17)-catalysed conversion into androgens.

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Section: Methodsmentioning

confidence: 99%

Specific accumulation of 17α-hydroxyprogesterone in microsomal membranes during the process of cytochrome P-450(C-17)-catalysed androgen biosynthesis. A dynamic study of intermediate formation and turnover

Kühn‐Velten

Lessmann

Förster

et al. 1988

Biochemical Journal

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Differential down-regulation and induction responses of testicular steroidogenic cytochromes P-450(cscc) and P-450(C17α) to human choriogonadotropin

1986

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Evidence is presented that the regulation of the cytochrome P-450(C17 alpha) of the steroid-17 alpha-monooxygenase and of the cytochrome P-450(cscc) of the cholesterol-monooxygenase by human choriogonadotropin (hCG) in vivo is mediated by differential mechanisms in the adult rat testis. An initial down-regulation of the cytochrome P-450(C17 alpha) but not of the P-450(cscc) can be demonstrated. Furthermore, induction of the cytochrome P-450(cscc) requires exposure to higher hCG doses (32% of the maximal induction rate of 43.7 pmol/(testis x d) are achieved with 4IU hCG/single dose) than induction of the P-450(C17 alpha) (59% of the maximal induction rate of 48.4 pmol/(testis x d) with 4IU hCG/single dose). Finally, induction of cytochrome P-450(cscc) starts faster after initiation of hCG treatment than induction of P-450(C17 alpha).

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Ketoconazole inhibition of the bifunctional cytochrome P450c17 does not affect androgen formation from the endogenous lyase substrate

Kühn‐Velten

Lessmann

1992

Biochemical Pharmacology

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Distribution of progesterone‐binding cytochrome P450 and steroid‐17α‐hydroxylase/C‐17,20‐lyase within different compartments of the rat testis

Cited by 7 publications

References 26 publications

Specific accumulation of 17α-hydroxyprogesterone in microsomal membranes during the process of cytochrome P-450(C-17)-catalysed androgen biosynthesis. A dynamic study of intermediate formation and turnover

Specific accumulation of 17α-hydroxyprogesterone in microsomal membranes during the process of cytochrome P-450(C-17)-catalysed androgen biosynthesis. A dynamic study of intermediate formation and turnover

Differential down-regulation and induction responses of testicular steroidogenic cytochromes P-450(cscc) and P-450(C17α) to human choriogonadotropin

Ketoconazole inhibition of the bifunctional cytochrome P450c17 does not affect androgen formation from the endogenous lyase substrate

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